The efficacy of intermittent intravenous cyclophosphamide in the treatment of rheumatoid arthritis will be evaluated in a double-blind randomized study. Patients unresponsive to conventional therapies will be assigned to receive a total of three intravenous infusions of either cyclophosphamide (1.0 gram per square meters, or less) or saline; one infusion every two months for a period of six months. The clinical activity of the arthritis and a functional assessment of patients will be quantitated during the study. Comparisons of the observed changes in these measures from assessments at the time of trial entry and two months after the final infusion will be made between treatment groups.